In the current art, drilling rigs or workover rigs with a hook capacity between 450 kips and 500 kips represent the upper limit for rigs with a mast and drawworks package that can be transported on a single trailer within legal or permit able road transportation limitations. Above this capacity, single trailer packaging is not achievable with a full-height mast with traveling equipment and a top drive pre-strung with wireline without grossly exceeding practical road weight limitations.
Although single trailer packaging of a mast is expected for smaller capacity operations for efficient mobilization, this upper limit capacity with the single trailer packaging presents compromises to design that distinguish the limited rig from a “full blown drilling rig”. Adherence to this type of packaging results in limitations of drawworks design, of working space on the floor, of mast flexibility, of mast durability, of mast stability, of floor height, of BOP height, and of allowable accessories. Extensive use of high-strength steel and extremely light design for components make the structural integrity inherently more critical or prone to and sensitive to damage that inevitably occurs in normal operations. Commonly, the mast or other components are removed and separately transported for legal road transport in many regions.
Many of the current single trailer or carrier rig designs treat the substructure somewhat as an afterthought. The packaging of the substructure for road transport, assembly, and erection is rarely given adequate attention.
In a fully capable, modern drilling package with a mud system with tanks, engine power and control modules, well control equipment, as well as other significant packages to complete, the mast and substructure represent only a portion of the total. Overall efficient packaging of the entire rig does not end with the mast and substructure.
One of the most notable deficiencies in mobile or “fast moving” rig packaging is the inability to move efficiently between wells a short distance apart. This major shortcoming is critical in some drilling operations that have wells in a cluster or single row. In these installations, the operator needs a rig to move very quickly (a few hours or less) between wells that are typically thirty meters or less apart from each other.
Most rig substructures are configured so that the rig must be completely rigged down to make these short moves. Other substructures have openings that allow skidding without rigging down, but have the disadvantage that the mast must be installed and laid down along the direction of the well row. This configuration is not acceptable because of the danger of the mast falling on a completed wellhead.
Current methods for modifying existing drilling rigs to allow them to move efficiently from well-to-well are very costly. The single trailer packaging does not lend itself to efficient well-to-well moves. The current art does not teach of any mobile or “fast moving” rigs that adequately address short well-to-well moves.
Some rig packages compromise on the mast height. Limitations to doubles or singles compromise on tripping efficiency and are not acceptable to many operators if a treble mast is available as an alternative.
A need, therefore, exists for a drilling rig that does not go beyond legal transportation limits, but also provides efficient installation and assembly, minimum rig up site requirement, scalability of rig capacity, mobility, well-to-well skidding, and winterization possibilities not found in the current art.